Maartje Boer

CROSS-NATIONAL VALIDATION OF THE SMD-SCALE 59 3 Cross-national Validation of the Social Media Disorder-Scale: Findings from Adolescents from 44 Countries Adolescents are the most digitally connected age group worldwide (Unicef, 2017). Research among European adolescents shows that between 2017 and 2019, 77% of 15- and 16-year-olds reported daily use of social media (Smahel et al., 2020), such as Instagram and Snapchat. However, concerns have been raised about adolescents who display symptoms of addiction regarding social media use (SMU) (La Barbera et al., 2009), such as being unable to control SMU, or by displacing other activities such as hobbies and sports for SMU (Griffiths et al., 2014; Van den Eijnden et al., 2016). However, diagnostic manuals, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), do not acknowledge social media addiction. Therefore, we refer to addiction-like SMU as problematic SMU . Cross-national data from the present Health Behaviour in School-aged Children (HBSC) study shows that, in 2017 and 2018, 4 to 18% of 15-year-olds reported problematic SMU (Inchley et al., 2020b). With an increasing body of evidence suggesting that problematic SMU threatens different aspects of adolescents’ wellbeing (Boer, Stevens, et al., 2020; Boer, Stevens, Finkenauer, De Looze, et al., 2021; Marino et al., 2018b; Piteo & Ward, 2020), different scales that measure problematic SMU have been developed. One of the most widely adopted scales is the Bergen Social Media Addiction Scale (Andreassen et al., 2016), which covers six items that parallel the core criteria of addiction, including preoccupation (i.e., salience), tolerance, withdrawal, persistence (i.e., relapse), escape (i.e., mood modification), and conflict (Griffiths, 2005; Griffiths et al., 2014). However, this conceptualization may not sufficiently measure the detrimental impact of this behavior for daily life, which is considered one of the core aspects of addiction-like behaviors (Kardefelt-Winther et al., 2017; Van Rooij et al., 2018). Another scale that measures problematic SMU is the nine-item Social Media Disorder (SMD)-scale (Boer, Stevens, Finkenauer, Koning, et al., 2021; Van den Eijnden et al., 2016). This scale includes the six core criteria and two additional criteria that measure detrimental consequences due to SMU, namely problems in important life domains and displacement of activities. In addition, it also includes the criterion deception . Together, these nine criteria